An open phase detecting system of a conventional electric vehicle control device obtains the average values Iu, Iv, and Iw of the respective phase currents of a three-phase AC current which is outputted by the inverter device, finds values Io=(Iu+Iv +Iw)/3 which result from further averaging the average values of those respective phase currents, and detects open phase when differences |Iu−Io|, |Iv−Io|, and |Iw−Io| between the average values of the respective phase currents and the further averaged value exceed a reference value.
Patent Document 1: JP 06-245301 A